TechCrunch broke the news today that Google has bought Gizmo5, the popular VoIP SIP provider, for $30 mil cash (not confirmed officially yet). The company was led by Michael Robertson, known for his times on mp3.com and Lindows. What does this mean for Google Voice? Read on.

Gizmo5 is one of the many providers for that protocol. Skype is the only one that uses its own protocol, and it's not compatible with the so-many SIP providers.

You create an account with Gizmo5 or other SIP providers, and then you can receive and make calls through the internet. The calls are free between the same provider, most of the time free between most SIP providers, but they do cost some money if you want to call Skype, or "real" landline/cellphone numbers.

Now, Google Voice is a "pairing" and "patching through" system. What it does is this: you create an account with them, and they give you a local phone number. Then, you "pair" that number with your real landline/cellphone number. When people are calling you on the GV number, you REAL landline/cellphone number will ring! See, if someone is calling you from Mongolia, and calls your GV number, because it's your GV number that patches you through to your real number, your telco only sees that local GV number, not the Mongolian one. And so you don't pay anything in your monthly bill! And you can initiate calls too, after you go to the GV web site and tell it "call this number, and make my real number ring". If the number you dialed is in the US, you pay nothing. If it's international, it's very cheap, about $0.2 per min. You can pair many "real" telephone/devices with GV, so it can ring all of them: your landline, your cellphone, your wife's cell etc. So no matter where you are, you are always going to receive the phone call, and it will always be seen as a local call.

Now, where it gets interesting is that you can "pair" GV with Gizmo5, which is an internet-only VoIP application. With this, you will get completely free calls, so you won't even be paying for local calls (e.g. as it is true in most cell contracts). And you can get someone on the other side of the planet, call your Gizmo number instead of your GV/landline/cellphone -- which will be free for him/her if he also uses Gizmo5 -- and then have it ring on any of your devices. Or, if you are vacating in Brazil, and you happen to have WiFi on your hotel, you will still get your calls, you won't miss a beat! You can use a Nokia S60 Symbian smartphone that has VoIP SIP support for example (since the iPhone doesn't support background apps, just PUSH doesn't work well with VoIP alerts)!

It's a bit complicated, I know. But take this with you: all this makes phone calls very cheap internationally, with the potential of becoming 100% free in a few years. Just like they don't pay anything on Star Trek to call each other, we won't either.

unless goverments buy out all the telcos i can't really see that 100% free calls happening ever, and even if you think they're free you'll still be paying for them, maybe just not by the minute...

do you really get charged different in the US if the calls comes from within the US or abroad? or is that just on cellphones since i think both parties pay for the calls over there, which would make more sense to me as to why google would need a SIP stack for google voice.

here in guatemala all the advantages you laid out would be moot since the calls are paid by whomever is making them only, so i wasn't seeing why would google need gizmo5

the thing i don't get is, considering how "cheap" it is to build a voip tisp why would they go out and buy one? what does gizmo5 have that no one else has or can't be build?